1. Field of the Invention
The present invention relates to a switching and connecting arrangement for coupling external and internal The invention also relates to an expansion card and a switching and connecting arrangement for it.
2. Description of Related Art
According to prior art, various electronic devices, such as portable personal computers (PC) are often provided with an expansion card connection, to which a standard expansion card can be connected. The expansion card may contain the radio parts of a wireless communication device with its internal antenna, wherein the PC may use this communication unit, or card-like wireless communication device, to communicate with a data transmission network. The expansion card can also constitute a network adapter, for example for a wireless local area network (WLAN). Said antennas are used for transmitting and receiving radio-frequency signals, and the signals are transferred between the radio part and the antenna by means of wires and connectors.
One known expansion card is a PC card complying with the PCMCIA standard (Personal Computer Memory Card International Association). Other known expansion cards include e.g. a so-called CompactFlash (CF) card according to the CFA standard (Compact Flash Association). For example for these CF cards, there are also adapters of the size of a PCMCIA card, in which the CF card is inserted for a PCMCIA connection.
A WLAN network adapter communicates directly with other devices or a local area network e.g. via an access point (AP). In a local area network of devices and a network adapter, arranged for example for a short-range data transmission connection (low power radio frequency, LPRF; short range radio frequency, SDRF), the frequency available is for example approximately 2.4 GHz, that is, 2400 MHz. An AP unit is typically used in public rooms and offices, wherein it is placed for example on a wall and an omnidirectional antenna is coupled to it. The network adapter can also be placed in an aircraft wireless LAN unit (AWLU) which is intended for fast wireless connection to the network of an aircraft during taxying and airport operations. In a home environment, the network adapter is located in an asymmetric digital subscriber line (ADSL) terminal which can be further used to set up e.g. a fast data transmission connection via a telephone network to the Internet network. A connection to the Internet network can also be set up by so-called portable web tablet devices which comprise a browser and communicate in a wireless manner with the terminal, e.g. a PC device, which is further connected to a LAN network or a telephone network. The terminal comprises a network adapter in a corresponding manner.
The requirements for operation of the above-described devices vary, wherein e.g. the properties and coverage areas of antennas vary and the environment affecting the operation of the antenna changes. Internal antennas on the circuit board of the card are, in some cases, placed wholly inside the terminals, which interferes with the reception and transmission of antenna signals. Thus, there is a need to use external antennas. In a network adapter installed in a stationary location, it is possible to use external antennas. These would be difficult to use if the expansion card is coupled e.g. to a portable device, wherein an internal antenna is better. If necessary, two antennas must be used, e.g. two internal antennas, to utilize the diversity.
For using various antennas, a variety of versions must be made of the expansion card, particularly of the circuit board to be placed in it, for different needs. It is difficult to arrange the manufacture and to estimate the need for different versions. External antennas are slightly used, wherein it is also expensive to arrange manufacture for a small need. The user will need several different expansion cards, if different antennas are required by varying use conditions, for example to secure a sufficiently long distance of transmission or reliable data transmission.
One known expansion card and its use is described in more detail e.g. in U.S. Pat. No. 5,809,115. An external antenna can be coupled to the expansion card by means of a connector. An expansion card is also known which is provided with a housing for an antenna at its end, wherein the antenna housing extends outside a PC device. The expansion card is at least partly placed inside the expansion card connection of the device. Another expansion card is disclosed in publication U.S. Pat. No. 5,628,055, wherein external antennas can be coupled to the end of a card, placed outside the card. U.S. Pat. No. 5,966,097 presents an expansion card comprising two L-shaped interted-F antennas (IFA) fitted on top of a circuit board used as a ground plane. Diversity is utilized by always coupling the antenna which is best suited for reception. The coupling is implemented with an antenna switch. To the antenna switch are connected the feed lines of both antennas and a line whereby the signals received by the antennas are fed to a transceiver.